I'm no SEO expert but try to do my own.
speed
- doing without the slider module that shows photos at the top is faster
- running the site through gtmetrix.com and checking what's a good photo resolution could help.
- Seen from the UK for the first time, the site had a kind of loading symbol that showed for a few seconds before I saw anything like a site. If that effects your US customers as well it could be bad for SEO
onpage
- google and bing webmaster tools are worth checking and then specialist seo scan sites
- the first specialised site I found is OK: seobility : it makes a lot of tiny suggestions that are either not do-able or don't seem important but you have to hope they add up. Free for first 1,000 scans. Ahrefs is similar but more of a puzzle. Theere are one or two other free but rather puzzling scan sites.
changing the site
This is a very specific idea that some people might like and others not.
I found a way to use the "manufacturers" module to write a page about each country of origin. I worked out how to put these "manufacturers" (I think Prestashop means brands) in a drop-down menu on the front page. It's easier to show than explain, and I'm on a variant of Prestashop 1.6 so I probably can't explain how to get the drop-down on the front page, but here's what it looks like: Veganline.com . I managed to get the left column to show on the front page and put a manufacturers block above a catagories block in the left column. It helps that the goods are from more than one country; maybe you could get one item from Canada or somewhere just to get people curious about the differences.
I've just typed what popped into my head that you quite likely know already. Hope it helps more than hinders.
John